1. Field of the Invention
The present general inventive concept relates to a method and apparatus to correct static deflection in a handling robot, and more particularly, to a method and apparatus to optimally correct static deflection caused by a weight of an end effector or a load on the end effector when the end effector is activated to handle large sheets of glass.
2. Description of the Related Art
Robots have been used for various purposes in various industrial fields. For example, the robots have been used to handle a sheet of glass in FDP fields such as LCD and PDP fields. The sheet of glass is loaded on a cassette called a glass buffer and is then delivered to each process area in a production line. A handling robot is used to remove the sheet of glass from the glass buffer in a unit process of the production line and then to load the sheet of glass back to the glass buffer after the sheet of glass is subjected to processing of the unit process.
Along with increased demands on flat display panels (FDPs), such as liquid crystal display panels (LCDs) and plasma display panels (PDPs), a size of a mother glass, which is a basic unit of FDP production, is increased to improve the productivity. Accordingly, a size of a handling robot for handling such glass is also increased since the productivity highly depends on the performance of the handling robot.
When the handling robot extends its end effector (or its hand) to handle a large sheet of glass, a weight of the end effector or a load on the end effector causes a large static deflection due to characteristics of the handling robot. If the static deflection is not minimized, a space for loading the glass may be increased, or the glass may be detached during handling, or the glass cannot be loaded on equipment under some circumstances, so that the glass cannot be used in the production line.
To overcome these problems, Korean Patent Publication No. 10-2000-21210 discloses a method for correcting static deflection in a robot.
In this correction method, a laser sensor attached to an end of the robot for object position correction is used to detect reference points of a current process object and a reference process object to set a corresponding object coordinate system, and a movement path of the robot is automatically corrected based on changes in a difference between the two coordinates.
Other methods have been used for correcting static deflection of large-size robots other than the glass handling robot. FIG. 1 illustrates a conventional static deflection correction method. Referring to FIG. 1, a position of an end effector 3 of a robot is measured in real time using a laser measurement apparatus 1 provided outside the robot, so that the position of the end effector 3 is controlled to correct static deflection of the end effector 3. A motor, such as a tilting mechanism 7, is provided on a reference point of a robot arm 5 to correct static deflection of the end effector 3.
However, in the conventional static deflection correction methods, the laser measurement apparatus 1 including a laser or the like cannot be installed in work areas of the robot due to characteristics of glass handling robots. Even if the static deflection of the end effector 3 is corrected using the laser measurement apparatus 1, a deflection angle of the end effector 3 cannot be corrected since general glass handling robots have no tilting mechanism 7 as shown in FIG. 1.
Even if the tilting mechanism 7 is installed in the glass handling robot, the angle of deflection of the end effector 3 in a specific direction (specifically, in an x direction) cannot be corrected. Also, the installation of the tilting mechanism 7 entails additional costs such as costs of the motor, and the laser measurement apparatus 1 and an apparatus provided for controlling the laser measurement apparatus 1 in real time also entail high additional costs.